1. Field of the Invention
The present invention relates to a method and a device for coating the junction area between at least two elongated elements. In particular, the present invention relates to a method and a device for coating the junction area between at least two elongated elements by application of an elastic tubular sleeve.
In more detail, the present invention relates to a method and a device, for coating the junction area between two electric cables.
It is a further object of the present invention to provide a joint for electric cables comprising a device for coating the junction area between said cables.
2. Description of the Related Art
In the specific case of junctions between electric cables, the device of the invention can be used for low-, medium- or high-voltage cables. Preferably, this device is used for coating the junction area between medium- and high-voltage cables.
Generally, application of an elastic tubular sleeve in the junction area between two elongated elements is obtained by use of a rigid tubular support that can be preferably separated into two halves, on which the sleeve is positioned in a radially expanded condition.
The sleeve expanded on said support is first fitted on one end of one of the elongated elements and, once junction of said elongated elements or of part of the constituent elements thereof has been carried out, the support is caused to slide on the elongated element until bringing the sleeve in register with the junction area itself.
In the preferred case in which the support consists of two halves, once the sleeve is positioned at the junction area, the two halves are released from each other and axially moved apart so as to enable the sleeve to adhere to the underlying elongated elements at the junction area of same.
The two halves, before separating and moving apart from each other, can be maintained in mutual engagement through different typologies of constraints or links.
For example, the European Patent EP 917,269 shows a “trigger” connection in which a toothed ring, made at one end of a first half, engages a corresponding circumferential groove made at the axially faced end of a second half.
To facilitate mutual separation of the two halves, use of auxiliary elongated elements is provided, each of which has a first portion extending along the outer surface of one half and inserted between said half and the sleeve fitted thereon, and a second portion, contiguous to the first one that, stepping over the end profile of said half, axially extends within the half itself, afterwards projecting at least partly from the axially opposite end.
The above mentioned European patent further describes a mutual engagement between the halves that is obtained through a circumferential weakening line defined by through holes of different sizes.
An alternative structure facilitating removal of the two halves is described in the European Patent EP 541,000 and the U.S. Pat. No. 6,472,600 both in the name of the same Applicant, according to which each half has a continuous helical cut defining a spiralled tape that is gradually removed by the operator by exerting a pulling action on the tape itself or on grip elements connected with said tape, said tape or grip elements such projecting from the outer end of each half that gradual removal of the support (and consequent collapsing of the sleeve on the junction area) is carried out starting from the centre of the junction area.
In said U.S. Pat. No. 6,472,600 it is further contemplated that one of the two halves be provided, at one of its ends, with a plurality of protuberances extending in an inclined direction relative to the longitudinal axis of the support, whereas the other half has a plurality of corresponding recesses matching the shape of said protuberances.
In this way the two halves are maintained in mutual engagement, forming a single piece until the moment the sleeve, that is disposed in an expanded condition on the corresponding support, is positioned at the junction area. Subsequently, at the moment said halves must be separated, it is required that one half be rotated relative to the other around its longitudinal axis to disengage the above mentioned protuberances from the respective recesses.
A further embodiment described in said US patent consists in providing a frangible ring for connection between the two support halves, said ring being obtained through formation of through slits or welding points. In compliance with this embodiment, separation of the two halves is achieved by use of a string fastened to the ring itself and pulling of which by the operator triggers breaking of said ring thereby causing mutual moving away of said halves in an axial direction.
In order to promote mutual moving apart of the two halves, and in particular sliding of the halves relative to the sleeve, use of a lubricating material interposed between the support and sleeve may be provided. This lubricating material is applied at the moment the sleeve is positioned on the support in an expanded condition.
The Applicant could ascertain that the technical solutions adopted in the known art to link the two support halves together are not able to ensure that the lubricating material will remain correctly positioned between the support and sleeve until the sleeve is applied onto the junction area. In fact it is to be noted that generally between manufacturing of the junction device and use of said device medium-long periods of time even in the order of some months may elapse.
In particular, the Applicant has ascertained that if a support previously made up of two parts or separable into two halves at the moment of being extracted, is wished to be used, the solutions known in the art contemplate circumferential discontinuities causing percolation of the lubricant through the faced surfaces of the two halves so that, as a result, the lubricant is no longer in the region where it had been originally applied.
Lack of lubrication, even if partial, during the support-ejection step represents an important problem because it causes an unacceptable increase in the ejection times and can even involve stopping of said step.